Hey,
I mainly browse this site from Firefox Mobile. The issues I noticed are as follows:
When adding something to a topic the textbox is behind the on screen keyboard making it very hard to know what you are writing. When creating a new topic this is not an issue.
When trying to reply to a specific post this only sometimes works correctly. I already deleted my post just to redo it exactly the same but with the correct linked reply.
Do you have similar Issues with the site on mobile?